diff --git a/ltr329.c b/ltr329.c
new file mode 100644
index 0000000..6918d7d
--- /dev/null
+++ b/ltr329.c
@@ -0,0 +1,202 @@
+/*
+ * ltr329.c
+ *
+ *  Created on: May 22, 2022
+ *      Author: david
+ */
+#include "ltr329.h"
+#include "main.h" /* for uart_disable_interrupts() */
+
+static int8_t ltr329_read_register (ltr329_cmd_t register_addr, uint8_t *register_data )
+{
+	uint8_t tx_buffer[1];
+	uint8_t rx_buffer[1];
+	int result;
+
+	// start measurement
+	tx_buffer[0] = register_addr;
+	/* disable interrupts to prevent modbus/i2c conflict */
+	uart_disable_interrupts();
+	result = i2c_transmit(LTR329_I2C_ADDRESS<<1, tx_buffer, 1);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return LTR329_ERROR;
+	}
+	LL_mDelay(10); /* 10 ms should be enough */
+	/* read out */
+	uart_disable_interrupts();
+	result = i2c_receive(LTR329_I2C_ADDRESS<<1, rx_buffer, 1);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return LTR329_ERROR;
+	}
+
+	*register_data = rx_buffer[0];
+	return LTR329_OK;
+}
+
+static int8_t ltr329_write_register (ltr329_cmd_t register_addr, uint8_t register_data)
+{
+	uint8_t tx_buffer[2];
+	int result;
+
+	// start measurement
+	tx_buffer[0] = register_addr;
+	tx_buffer[1] = register_data;
+	/* disable interrupts to prevent modbus/i2c conflict */
+	uart_disable_interrupts();
+	result = i2c_transmit(LTR329_I2C_ADDRESS<<1, tx_buffer, 2);
+	uart_enable_interrupts();
+	if (result != I2C_OK) {
+		return LTR329_ERROR;
+	}
+	return LTR329_OK;
+}
+
+int8_t ltr329_write_settings (ltr329_gain_t gain, ltr329_als_mode_t mode, ltr329_integration_time_t integ_time, ltr329_measurement_rate_t meas_rate)
+{
+	int8_t result;
+	/* Write Gain and ALS Mode */
+	result = ltr329_write_register(LTR329_ALS_CONTR, (gain | mode));
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	/* Write Integration Time and Measurement Rate */
+
+	result = ltr329_write_register(LTR329_ALS_MEAS_RATE, (integ_time | meas_rate));
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	return LTR329_OK;
+}
+
+int8_t ltr329_read_settings (ltr329_gain_t *gain, ltr329_als_mode_t *mode, ltr329_integration_time_t *integ_time, ltr329_measurement_rate_t *meas_rate)
+{
+	int8_t result;
+	uint8_t control_register_data;
+	uint8_t rate_register_data;
+
+	result = ltr329_read_register(LTR329_ALS_CONTR, &control_register_data);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+
+	result = ltr329_read_register(LTR329_ALS_MEAS_RATE, &rate_register_data);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+
+	uint8_t control_register_gain_mask = 0b00011100;
+	uint8_t control_register_mode_mask = 0b00000001;
+	uint8_t rate_register_int_time_mask = 0b00111000;
+	uint8_t rate_register_rate_mask = 0b00000111;
+
+	/* Return Registers Values */
+	/* TODO: This might not be safe */
+	*gain = control_register_data & control_register_gain_mask;
+	*mode = control_register_data & control_register_mode_mask;
+	*integ_time = rate_register_data & rate_register_int_time_mask;
+	*meas_rate = rate_register_data & rate_register_rate_mask;
+
+	return LTR329_OK;
+}
+
+int8_t ltr329_sw_reset( void )
+{
+	int8_t result;
+	/* Write Gain and ALS Mode */
+	result = ltr329_write_register(LTR329_ALS_CONTR, 0b00000010);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	return LTR329_OK;
+}
+
+int8_t ltr329_measure (uint16_t *data_ch0, uint16_t *data_ch1)
+{
+	uint8_t ch0_l, ch0_h, ch1_l, ch1_h;
+	int result;
+	result = ltr329_read_register(LTR329_ALS_DATA_CH0_0, &ch0_l);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	result = ltr329_read_register(LTR329_ALS_DATA_CH0_1, &ch0_h);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	result = ltr329_read_register(LTR329_ALS_DATA_CH1_0, &ch1_l);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	result = ltr329_read_register(LTR329_ALS_DATA_CH1_1, &ch1_h);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+
+	*data_ch0 = (ch0_h << 8) + ch0_l;
+	*data_ch1 = (ch1_h << 8) + ch1_l;
+	return LTR329_OK;
+}
+
+int8_t ltr329_read_status_register(uint8_t *data_valid, uint8_t *new_data, ltr329_gain_t *gain)
+{
+	int8_t result;
+	uint8_t status_register_data;
+	result = ltr329_read_register(LTR329_ALS_STATUS, &status_register_data);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+
+	/* Check data valid */
+	uint8_t data_invalid_mask = 0b10000000;
+	if ((status_register_data & data_invalid_mask) == data_invalid_mask)
+	{
+		*data_valid = 0;
+	} else
+	{
+		*data_valid = 1;
+	}
+
+	/* Check if there is new data */
+	uint8_t data_status_mask = 0b00000100;
+	if ((status_register_data & data_status_mask) == data_status_mask)
+	{
+		*new_data = 1;
+	} else
+	{
+		*new_data = 0;
+	}
+
+	/* Check Gain */
+	/* TODO: This might not be safe */
+	uint8_t gain_mask = 0b01110000;
+	*gain = status_register_data & gain_mask;
+
+	return LTR329_OK;
+}
+
+int8_t ltr329_read_device_info (uint8_t *manufacturer_id, uint8_t *part_id)
+{
+	int8_t result;
+	result = ltr329_read_register(LTR329_MANUFAC_ID, manufacturer_id);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	result = ltr329_read_register(LTR329_PART_ID, part_id);
+	if (result != LTR329_OK)
+	{
+		return LTR329_ERROR;
+	}
+	return LTR329_OK;
+}
diff --git a/ltr329.h b/ltr329.h
new file mode 100644
index 0000000..7294a2a
--- /dev/null
+++ b/ltr329.h
@@ -0,0 +1,93 @@
+/*
+ * ltr329.h
+ *
+ *  Created on: May 22, 2022
+ *      Author: david
+ */
+
+#ifndef INC_LTR329_H_
+#define INC_LTR329_H_
+
+#include "stdint.h"
+#include "stm32l0xx_ll_i2c.h"
+#include "stm32l0xx_ll_utils.h"
+#include "i2c.h"
+
+#define LTR329_I2C_ADDRESS 0x29
+
+/*
+ * Return values
+ */
+
+#define LTR329_OK 0
+#define LTR329_ERROR -1 // generic error
+
+/* LTR-329ALS-01 Registers */
+/* Datasheet: https://optoelectronics.liteon.com/upload/download/DS86-2014-0006/LTR-329ALS-01_DS_V1.pdf */
+typedef enum
+{
+	LTR329_ALS_CONTR 			= 0x80,	/* RW */
+	LTR329_ALS_MEAS_RATE 		= 0x85, /* RW */
+	LTR329_PART_ID 				= 0x86, /* R */
+	LTR329_MANUFAC_ID 			= 0x87, /* R */
+	LTR329_ALS_DATA_CH1_0 		= 0x88, /* R */
+	LTR329_ALS_DATA_CH1_1 		= 0x89, /* R */
+	LTR329_ALS_DATA_CH0_0 		= 0x8A, /* R */
+	LTR329_ALS_DATA_CH0_1 		= 0x8B, /* R */
+	LTR329_ALS_STATUS 			= 0x8C /* R */
+} ltr329_cmd_t;
+
+/* Bit masks for ALS Mode */
+typedef enum
+{
+	LTR329_MODE_STAND_BY		= 0b00000000, /* DEFAULT */
+	LTR329_MODE_ACTIVE			= 0b00000001
+} ltr329_als_mode_t;
+
+/* Bit masks for Gain settings */
+typedef enum
+{
+	LTR329_GAIN_1X 				= 0b00000000, /* DEFAULT */
+	LTR329_GAIN_2X				= 0b00000100,
+	LTR329_GAIN_4X				= 0b00001000,
+	LTR329_GAIN_8X				= 0b00001100,
+	LTR329_GAIN_48X				= 0b00011000,
+	LTR329_GAIN_96X				= 0b00011100,
+	LTR329_GAIN_RESERVED1		= 0b00010000,
+	LTR329_GAIN_RESERVED2		= 0b00010100
+} ltr329_gain_t;
+
+/* Bit masks for Integration Time settings */
+typedef enum
+{
+	LTR329_INTEGRATION_50MS		= 0b00001000,
+	LTR329_INTEGRATION_100MS 	= 0b00000000, /* DEFAULT */
+	LTR329_INTEGRATION_150MS	= 0b00100000,
+	LTR329_INTEGRATION_200MS	= 0b00010000,
+	LTR329_INTEGRATION_250MS	= 0b00101000,
+	LTR329_INTEGRATION_300MS	= 0b00110000,
+	LTR329_INTEGRATION_350MS	= 0b00111000,
+	LTR329_INTEGRATION_400MS	= 0b00011000
+} ltr329_integration_time_t;
+
+/* Bit masks for Measurement Rate settings */
+typedef enum
+{
+	LTR329_MEAS_RATE_50MS		= 0b00000000,
+	LTR329_MEAS_RATE_100MS		= 0b00000001,
+	LTR329_MEAS_RATE_200MS		= 0b00000010,
+	LTR329_MEAS_RATE_500MS		= 0b00000011, /* DEFAULT */
+	LTR329_MEAS_RATE_1000MS		= 0b00000100,
+	LTR329_MEAS_RATE_2000MS		= 0b00000111
+} ltr329_measurement_rate_t;
+
+static int8_t ltr329_read_register (ltr329_cmd_t register_addr, uint8_t *register_data );
+static int8_t ltr329_write_register (ltr329_cmd_t register_addr, uint8_t register_data);
+int8_t ltr329_write_settings (ltr329_gain_t gain, ltr329_als_mode_t mode, ltr329_integration_time_t integ_time, ltr329_measurement_rate_t meas_rate);
+int8_t ltr329_read_settings (ltr329_gain_t *gain, ltr329_als_mode_t *mode, ltr329_integration_time_t *integ_time, ltr329_measurement_rate_t *meas_rate);
+int8_t ltr329_sw_reset( void );
+int8_t ltr329_measure (uint16_t *data_ch0, uint16_t *data_ch1);
+int8_t ltr329_read_status_register(uint8_t *data_valid, uint8_t *new_data, ltr329_gain_t *gain);
+int8_t ltr329_read_device_info (uint8_t *manufacturer_id, uint8_t *part_id);
+
+#endif /* INC_LTR329_H_ */